While the principles of the present invention can be applied to many types of surgical stapling instruments provided with scalpel means, for purposes of an exemplary showing, the invention will be described in terms of an annular, washer-like backup means for a surgical stapling instrument having a cylindrical scalpel. In recent years there has been an ever increasing use of surgical staples, in lieu of conventional sutures, in many internal organ and intestinal procedures ranging from the esophagus to the rectum. U.S. Pat. Nos. 3,193,165; 3,388,847; 3,552,626, together with copending application Ser. No. 124,954, filed Feb. 26, 1980,; in the name of Robert G. Rothfuss and entitled INTRALUMENAL ANASTOMOSIS SURGICAL STAPLING INSTRUMENT teach exemplary types of surgical stapling instruments devised by prior art workers for such procedures. The use of surgical staples and such surgical stapling instruments has made many difficult procedures much simpler and has significantly reduced the time required for such procedures. This is of importance in that it significantly reduces the length of time for which the patient must be maintained under anesthetic.
Each of the exemplary above mentioned patents and copending application teaches a surgical stapling instrument provided with a cylindrical scalpel and a washer-like backup element for the scalpel made of semi-rigid material. Each of these instruments has a casing or head containing at least one annular array of surgical staples. The cylindrical scalpel and a driver for the surgical staples are normally located within the head. The staple driver and the cylindrical scalpel are actuated by a manually operable lever.
These instruments all have the disadvantage of requiring a high force to embed the cylindrical scalpel into the semi-rigid backup washer. The actual force required is proportional to the depth of penetration of the cylindrical scalpel into the washer. The deeper the scalpel penetrates the washer, the more force is required and this prevents any tactile feed back to the surgeon. As a result, the surgeon never knows from the "feel" of the instrument whether or not the staples have been implanted and clinched or the excess tissue of the tubular organs being joined has been completely excised since the lever of the instrument is usually squeezed to refusal.
The present invention is directed to a cut-through backup washer, the proximal end of which faces the cylindrical scalpel. The cut-through washer comprises inner and outer annular walls joined together at their proximal ends by a thin web providing a backup surface for the cylindrical scalpel. This structure has the advantage that minimal force is used to excise the tissue and as the thin web of the cut-through washer is thereafter severed by the cylindrical scalpel, the force required at the lever of the instrument is abruptly reduced. This abrupt reduction of lever force gives the surgeon a clear and unmistakable tactile signal that the surgical staples have been formed and that the excess tissue of the tubular body organs being joined has been excised by the cylindrical scalpel. Thus, in addition to this tactile signal, the backup washer of the present invention reduces the peak force and work required for the tissue cutting portion of the anastomotic procedure.
The above mentioned copending application teaches an intraluminal anastomosis surgical stapling instrument which will adequately and reliably clinch surgical staples of a predetermined leg length over a working gap between the staple containing casing and the anvil of at least two millimeters. The cut-through backup washer of the present invention is particularly advantageous in such a surgical stapling instrument since the depth of penetration of the backup washer by the cylindrical scalpel required particularly at the minimum end of the working gap of the instrument is considerable. This, in turn, would require considerable force at the lever of the instrument. When this instrument is provided with the cut-through backup washer of the present invention the force required at the lever is greatly reduced and is the same throughout the working gap of the instrument, as will be described hereinafter.